Reinforcing materials such as organic fiber codes and steel codes have been widely used hitherto in rubber-based composite materials for use in tire, belt, hose, and the like. In such a case, it is very important that the rubber and the reinforcing material bind to each other firmly, from the viewpoints of the durability and the morphological stability of product. For example, in composite materials of an organic fiber code and a rubber, the organic fiber code is commonly dipped in an resorcin-formaldehyde condensate/latex (RFL) adhesive for improvement in adhesion between the two, while in composite materials of a steel code and a rubber, the steel code is plated in various ways for improvement in adhesion between the two.
In this manner, there are a variety of ways to improve the adhesiveness between a rubber composition and a reinforcing material, and such composite materials higher in adhesiveness should ideally be superior both the initial adhesiveness and the adhesion durability.